The four major objectives of this Rocky Mountain spotted fever (RMSF) project on Cape Cod, Massachusetts, include 1. to characterize the clinical and serologic features of acute RMSF in dogs and the role of dogs in the transmission of RMSF to man; 2. to locate and define the boundaries of suspected foci of ticks infected with RMSF on Cape Cod; 3. to design models for control or prevention of RMSF on Cape Cod through dog and/or tick control, and 4. to design a model for effective study of RMSF elsewhere in the USA. Several thousand Cape Cod dogs will be surveyed for RMSF residual antibodies. During the active tick season (April-July) intensive studies will be undertaken to investigate sick dogs and demonstrate RMSF infection by embryonated egg or guinea pig isolation techniques. Ticks taken from infected dogs will be studied carefully for infection. Relations of these dogs, their ticks, and man will be correlated. Residual RMSF titers of dogs, as well as acute RMSF attacks in dogs will be charted geographically to locate nidi of infected ticks. Information gained from dogs and ticks will be used to control or eliminate infected tick foci and design RMSF study models for other areas of the USA.